Automated techniques for printer system output quality assurance and component failure detection provide improved printer system reliability. Errors in photoreceptor motion quality can often result in density non-uniformities in the direction of the printing process on the printed page. Due to the mechanical design of printing systems, these defects (often referred to as “bands”) are often periodic in nature resulting in a “banding” defect appearing on the printed page. Numerous techniques have been developed for measuring banding sources in an effort to deal with banding defects. Many of these techniques involve the use of halftone targets to directly measure banding density variations while others measure banding by using ladder charts to measure variations in photoreceptor surface velocity.
Printing ladder charts can give very accurate photoreceptor velocity measurements but are mainly useful for banding sources that result in photoreceptor surface velocity variations. Such banding sources include: deterioration in the performance of the photoreceptor motor, gear, gear teeth; drive train run out and tolerances; servo control or stepper motor control errors; and photoreceptor surface out-of-round errors particularly as the photoreceptor surface wears with component age.
Current techniques for photoreceptor motion quality estimation through the use of printed ladder charts are limited to analysis of relatively high photoreceptor velocity variation frequencies with poor frequency resolution due to the limited data length available by printing a single page. Some printer systems have photoreceptors that are many pages long. As such, analyzing banding on a single page provides information for only a fraction of photoreceptor revolution. Other printing systems that use, for example, a drum photoreceptor, may capture only a few revolutions of the photoreceptor drum. Printing and analyzing a longer page, such as an 11″×17″ page, can provide more information, but the limited length of banding data can limit frequency resolution and accuracy at low banding frequencies, which are limitations of analysis using a single printed page.
Accordingly, what is needed in this art are increasingly sophisticated systems and methods for analyzing photoreceptor motion quality in a document reproduction system.